Waste energy recovery method and waste energy recovery system

ABSTRACT

An oil cooler for cooling hydraulic oil that has increased in temperature due to energy loss in a hydraulic circuit a radiator for cooling engine cooling water that has increased in temperature as a result of cooling an engine and an ATAAC for cooling engine intake air that has increased in temperature as a result of being compressed by a turbocharger, are provided with heat pipes for vaporizing low-boiling medium by absorbing heat from the oil cooler the radiator and the ATAAC. A power recovery turbine is rotated by energy provided by vaporized low-boiling medium is provided for the engine. A low-boiling medium circuit is provided so as to drive the turbine by feeding the low-boiling medium that has been vaporized by waste heat energy. The low-boiling medium circuit includes the heat pipes of the oil cooler the radiator, and the ATAAC, as well as the turbine.

CROSS-REFERENCE TO PRIOR APPLICATION

This is a U.S. National Phase Application under 35 U.S.C. §371 ofInternational Patent Application No. PCT/JP2005/006628, filed Apr. 5,2005, and claims the benefit of Japanese Patent Application No.2004-273991, filed Sep. 21, 2004, both of which are incorporated byreference herein. The International Application has not published yet atthe time of filing of this application.

TECHNICAL FIELD

1. Field of the Invention

The present invention relates to a waste heat energy recovery method anda waste heat energy recovery system for recovering waste heat energygenerated from a hydraulic circuit or any other similar system.

2. Background Art

A conventional construction machine typically has such a configurationthat power is supplied from an engine, which is normally a dieselengine, to a main pump so that pressurized oil is fed from the main pumpto actuator control valves.

An actuator that has been supplied with pressurized oil fed from thecorresponding actuator control valve performs a certain net amount ofwork on an external entity, while the remaining energy is transformed tothermal energy that is dispersed into the air, as it is lost throughvarious relief valves, reduction of the internal area of the controlvalve, and piping resistance.

An oil cooler is provided to reduce the temperature of the hydraulicoil, because a rise in the temperature of the hydraulic oil causesthermal degradation of the oil as well as a decrease in its viscosity,resulting in damage to hydraulic equipment. However, the engine has tosupply additional power to drive a rotary fluid cooling machine, such asa cooling fan, for cooling the radiation fins of the oil coolerexternally (e.g. see Japanese Laid-open Patent Publication No.2000-257608 (pp 3, FIG. 2)).

The abovementioned conventional art is explained hereunder, referring toFIG. 2. A main pump 12 driven by a diesel engine 11 discharges oil,which is fed as pressurized oil through a check valve 12 a to anactuator control valve 13. The pressurized oil is fed from the actuatorcontrol valve 13 through a pipeline 14 a to an actuator 14 so that theactuator 14 performs a certain net amount of work on an external entity.Due to energy loss through heat generation by the actuator 14, variousrelief valves 15, internal area reduction R1 of the actuator controlvalve 13, and piping resistance R2 of the pipeline 14 a, etc., theremaining energy is transformed to thermal energy, most of which isdispersed as a result of increasing the temperature of the hydraulicoil.

As a rise in the temperature of the hydraulic oil causes thermaldegradation of the oil as well as a decrease in its viscosity, resultingin shorter life of hydraulic equipment, the radiation fins of an oilcooler 16 a are air-cooled by a cooling fan 18, which is driven by anexternally provided hydraulic cooling motor 17 in order to reducetemperature of the hydraulic oil. In order to drive the hydrauliccooling motor 17, a hydraulic cooling pump 19 is provided, with itsgears adapted to be driven by the engine 11 so that pressurized oil isfed from the hydraulic cooling pump 19 to the hydraulic cooling motor17. Therefore, the engine 11 is required to supply power in addition tothe power supplied to the main pump 12.

Similar energy loss also occurs in the cooling system of the engine 11,in which fossil fuel, such as diesel oil, burns to generate energy to besupplied in the form of shaft power to the pump system. As much of theenergy that is not consumed as the shaft power becomes thermal energyand increases the temperature of engine cooling water, the cooling fan18, which is driven by the aforementioned hydraulic cooling motor 17,cools by means of air the radiation fins of a radiator 16 b in order toreduce the temperature of the engine cooling water. As a result, thethermal energy dissipates in the air through the radiation fins of theradiator 16 b. The radiator 16 b is a heat exchanger provided in theengine cooling water circuit.

Furthermore, as the temperature of the engine intake air that has beenpressurized by a turbocharger (not shown) provided in an engine intakesystem becomes high, the cooling fan 18, which is driven by thehydraulic cooling motor 17, cools by means of air the radiation fins ofan air-to-air after-cooler (hereinafter referred to as ATAAC) 16 c inorder to cool the engine intake air, thereby increasing the air intakeefficiency of the engine 11, as well as reducing combustion temperatureso as to reduce the amount of nitrogen oxides generated. As a result,the thermal energy of the pressurized engine intake air dissipates inthe air through the radiation fins of the ATAAC 16 c, which is providedin an intercooler circuit.

As described above, the radiation fins of the oil cooler 16 a, theradiation fins of the radiator 16 b, and the radiation fins of the ATAAC16 c are air-cooled by the cooling fan 18, which is driven by theexternally provided hydraulic cooling motor 17, in order to reduce thetemperatures of the hydraulic oil and other fluids, i.e. the enginecooling water and the engine intake air. In order to drive the hydrauliccooling motor 17, the aforementioned hydraulic cooling pump 19 isprovided, separately from the main pump 12, in a pump assembly attachedto an output shaft of the engine 11, so as to feed pressurized oil fromthe hydraulic cooling pump 19 to the hydraulic cooling motor 17.

Therefore, the engine 11 is required to supply power in addition to thepower supplied to the main pump 12. Moreover, thermal energy dissipatesin the air through the radiation fins of the oil cooler 16 a, which is aheat exchanger, as well as the radiation fins of the radiator 16 b andATAAC 16 c.

This presents the problem of substantial power loss of the engine 11,resulting in very poor energy use efficiency.

In FIG. 2, which provides an example using concrete values to explainthe above problem, 95% of the shaft output power of the engine 11 is theeffective shaft input power to the main pump 12, while the remaining 5%is the effective shaft input power to the hydraulic cooling pump 19.

In order to solve the above problem, an object of the present inventionis to improve the energy use efficiency of the engine.

SUMMARY OF THE INVENTION

The present invention provides a waste heat energy recovery method forrecovering waste heat energy by using a low-boiling medium to absorbwaste heat energy from hydraulic oil that has increased in temperatureas a result of loss of energy in a hydraulic circuit that includes apump adapted to be driven by an engine, as well as waste heat energyfrom another fluid that has increased in temperature as a result ofoperation of the engine, and rotating a power recovery turbine byutilizing the low-boiling medium that has vaporized as a result ofabsorbing the heat so as to boost the power of the engine by means ofthe turbine. By transferring waste heat energy to the low-boiling mediumfrom the hydraulic oil that has increased in temperature as a result ofloss of energy in the hydraulic circuit as well the other fluid that hasincreased in temperature as a result of operation of the engine, thehydraulic oil and the other fluid are cooled while the low-boilingmedium is vaporized, so that the vaporized low-boiling medium rotatesthe turbine, which then provides a boost to the engine and therebyrecovers the waste heat energy. As a part of the lost engine power,which would, in case of a conventional art, wastefully dissipate intothe air as waste heat energy of the hydraulic oil and the other fluid,is effectively recirculated to the engine through the turbine, theenergy use efficiency of the engine is improved.

The present invention also provides a waste heat energy recovery systemhaving an oil cooler, another cooling means, a power recovery turbine,and a low-boiling medium circuit. The oil cooler serves to coolhydraulic oil that has increased in temperature as a result of loss ofenergy in a hydraulic circuit that includes a pump adapted to be drivenby an engine. The other cooling means serves to cool another fluid thathas increased in temperature as a result of operation of the engine. Theaforementioned turbine is provided for the engine and adapted to berotated by energy provided by a vaporized low-boiling medium. Thelow-boiling medium circuit serves to drive the turbine by providing theturbine with the low-boiling medium that has been vaporized by wasteheat energy from the oil cooler and the other cooling means. With theconfiguration as above, by transferring waste heat energy to thelow-boiling medium from the hydraulic oil that has increased intemperature as a result of loss of energy in the hydraulic circuit aswell as the other fluid that has increased in temperature as a result ofoperation of the engine, the hydraulic oil and the other fluid arecooled while the low-boiling medium is vaporized. And by providing theturbine with the vaporized low-boiling medium through the low-boilingmedium circuit in order to drive the turbine so that the turbineprovides a boost to the engine and thereby recovers the waste heatenergy. As a part of the lost engine power, which would, in case of aconventional art, wastefully dissipate into the air as waste heat energyfrom the oil cooler and the other cooling means, is effectivelyrecirculated to the engine by means of the low-boiling medium circuitand the turbine, the energy use efficiency of the engine is improved.

According to another feature of the present invention, theaforementioned other cooling means of a waste heat energy recoverysystem is a radiator for cooling engine cooling water that has increasedin temperature as a result of cooling the engine. With the configurationas above, by transferring waste heat energy from the hydraulic oil andengine cooling water to the low-boiling medium, the hydraulic oil andthe engine cooling water are cooled while the low-boiling medium isvaporized. And by providing the turbine with the vaporized low-boilingmedium through the low-boiling medium circuit in order to drive theturbine so that the turbine provides a boost to the engine and therebyrecovers the waste heat energy. As a part of the lost engine power,which would, in case of a conventional art, wastefully dissipate intothe air as waste heat energy from the oil cooler and the radiator, iseffectively recirculated to the engine by means of the low-boilingmedium circuit and the turbine, the energy use efficiency of the engineis improved.

According to yet another feature of the present invention, theaforementioned other cooling means of a waste heat energy recoverysystem as claimed in claim 2 is an intake air cooler for cooling engineintake air that has increased in temperature as a result of beingcompressed by a turbocharger. With the configuration as above, bytransferring waste heat energy to the low-boiling medium from thehydraulic oil that has increased in temperature as a result of loss ofenergy in the hydraulic circuit as well as the engine intake air thathas increased in temperature as a result of being compressed by theturbocharger, the hydraulic oil and the engine intake air are cooledwhile the low-boiling medium is vaporized. And by providing the turbinewith the vaporized low-boiling medium through the low-boiling mediumcircuit in order to drive the turbine so that the turbine provides aboost to the engine and thereby recovers the waste heat energy. As apart of the lost engine power, which would, in case of a conventionalart, wastefully dissipate into the air as waste heat energy from the oilcooler and the intake air cooler, is effectively recirculated to theengine by means of the low-boiling medium circuit and the turbine, theenergy use efficiency of the engine is improved.

According to yet another feature thereof, the present invention providesa waste heat energy recovery system having an oil cooler, a radiator, anintake air cooler, a power recovery turbine, and a low-boiling mediumcircuit. The oil cooler serves to cool hydraulic oil that has increasedin temperature as a result of loss of energy in a hydraulic circuit thatincludes a pump adapted to be driven by an engine. The radiator servesto cool engine cooling water that has increased in temperature as aresult of cooling the engine. The intake air cooler serves to coolengine intake air that has increased in temperature as a result of beingcompressed by a turbocharger. The aforementioned turbine is provided forthe engine and adapted to be rotated by energy provided by a vaporizedlow-boiling medium. The low-boiling medium circuit serves to drive theturbine by providing the turbine with the low-boiling medium that hasbeen vaporized by waste heat energy from the oil cooler, the radiator,and the intake air cooler. With the configuration as above, bytransferring waste heat energy to the low-boiling medium from thehydraulic oil that has increased in temperature as a result of loss ofenergy in the hydraulic circuit, the engine cooling water that hasincreased in temperature as a result of cooling the engine, and alsofrom the engine intake air that has increased in temperature as a resultof being compressed by the turbocharger, the hydraulic oil, the enginecooling water, and the engine intake air are cooled while thelow-boiling medium is vaporized. And by providing the turbine with thevaporized low-boiling medium through the low-boiling medium circuit inorder to drive the turbine so that the turbine provides a boost to theengine and thereby recovers the waste heat energy. As a part of the lostengine power, which would, in case of a conventional art, wastefullydissipate into the air as waste heat energy from the oil cooler, theradiator, and the intake air cooler, is effectively recirculated to theengine by means of the low-boiling medium circuit and the turbine, theenergy use efficiency of the engine is improved.

According to yet another feature of the present invention thelow-boiling medium circuit includes heat pipes, a feed line, and areturn line, the aforementioned heat pipes serving to permit a part ofthe low-boiling medium fed from a low-boiling medium pump to anevaporator of an air conditioning device circuit to branch off from theair conditioning device circuit and pass through the oil cooler and theother cooling means so that the low-boiling medium vaporizes byabsorbing heat from the oil cooler and the other cooling means, theaforementioned air conditioning device circuit including a compressor, acondenser, a receiver, the aforementioned low-boiling medium pump, anexpansion valve, and the aforementioned evaporator, all of which areinstalled in a construction machine and connected to one another in anendless circuit, the aforementioned feed line serving to provide theturbine with low-boiling medium that has been vaporized inside the heatpipes, and the aforementioned return line serving to recirculate thelow-boiling medium from the turbine to the intake end of the compressorof the air conditioning device circuit. With the configuration as above,when a part of the low-boiling medium fed to the evaporator of the airconditioning device circuit installed in the construction machinebranches off and passes through the heat pipes, the waste heat energy ofthe hydraulic oil that has increased in temperature as a result of lossof energy as well as the other fluid that has increased in temperatureas a result of operation of the engine is transferred to theaforementioned part of the low-boiling medium. As a result, thehydraulic oil and the other fluid are cooled while the low-boilingmedium in the heat pipes is vaporized, the vaporized low-boiling mediumis fed through the feed line to the turbine and thereby drives theturbine, and the low-boiling medium from the turbine is recirculatedthrough the return line to the intake end of the compressor. As theconfiguration described above enables an air conditioning device circuitto be provided at lower cost by effectively using a part of the airconditioning device circuit already incorporated in the constructionmachine, eliminates the necessity of conventional expensive components,such as a cooling motor and a cooling pump for driving a cooling fan,and also eliminates the power loss resulting from driving the coolingpump, the configuration described above is cost effective.

According to yet another feature of the present invention theaforementioned turbine is connected to a power transmission system,which branches off from a power transmission unit that enables theengine to drive the pump. By using the power transmission system, whichbranches off from the power transmission unit that enables the engine todrive the pump, the configuration described above facilitatesinstallation of the turbine. Furthermore, by driving the turbine bymeans of the low-boiling medium vapor that has been vaporized by thewaste heat energy from the oil cooler and the waste heat energy from theother cooling means, and feeding driving torque generated in the turbineto the engine through the power transmission system, the configurationdescribed above reduces the driving power of the engine to drive thepump, thereby enabling reduction of fuel consumption by the engine, aswell as effective recovery of thermal energy lost in the hydrauliccircuit.

According to the present invention by transferring waste heat energy toa low-boiling medium from the hydraulic oil that has increased intemperature as a result of loss of energy in the hydraulic circuit aswell as the other fluid that has increased in temperature as a result ofoperation of the engine, the hydraulic oil and the other fluid arecooled while the low-boiling medium is vaporized, so that the vaporizedlow-boiling medium rotates the turbine, which then provides a boost tothe engine and thereby recovers the waste heat energy. As a part of thelost engine power, which would, in case of a conventional art,wastefully dissipate from the hydraulic oil and the other fluid into theair as waste heat energy, can be effectively recirculated to the enginethrough the turbine, the energy use efficiency of the engine can beimproved.

According to another feature of the present invention by transferringwaste heat energy to the low-boiling medium from the hydraulic oil thathas increased in temperature as a result of loss of energy in thehydraulic circuit as well as the other fluid that has increased intemperature as a result of operation of the engine, the hydraulic oiland the other fluid are cooled while the low-boiling medium isvaporized. And by providing the turbine with the vaporized low-boilingmedium through the low-boiling medium circuit in order to drive theturbine so that the turbine provides a boost to the engine and therebyrecovers the waste heat energy. As a part of the lost engine power,which would, in case of a conventional art, wastefully dissipate intothe air as waste heat energy from the oil cooler and the other coolingmeans, can be effectively recirculated to the engine by means of thelow-boiling medium circuit and the turbine, the energy use efficiency ofthe engine can be improved.

According to yet another feature of the present invention bytransferring waste heat energy from the hydraulic oil and engine coolingwater to the low-boiling medium, the hydraulic oil and the enginecooling water are cooled while the low-boiling medium is vaporized. Andby providing the turbine with the vaporized low-boiling medium throughthe low-boiling medium circuit in order to drive the turbine so that theturbine provides a boost to the engine and thereby recovers the wasteheat energy. As a part of the lost engine power, which would, in case ofa conventional art, wastefully dissipate into the air as waste heatenergy from the oil cooler and the radiator, can be effectivelyrecirculated to the engine by means of the low-boiling medium circuitand the turbine, the energy use efficiency of the engine can beimproved.

According to yet another feature of the present invention bytransferring waste heat energy to the low-boiling medium from thehydraulic oil that has increased in temperature as a result of loss ofenergy in the hydraulic circuit as well as the engine intake air thathas increased in temperature as a result of being compressed by theturbocharger, the hydraulic oil and the engine intake air are cooledwhile the low-boiling medium is vaporized. And by providing the turbinewith the vaporized low-boiling medium through the low-boiling mediumcircuit in order to drive the turbine so that the turbine provides aboost to the engine and thereby recovers the waste heat energy. As apart of the lost engine power, which would, in case of a conventionalart, wastefully dissipate into the air as waste heat energy from the oilcooler and the intake air cooler, can be effectively recirculated to theengine by means of the low-boiling medium circuit and the turbine, theenergy use efficiency of the engine can be improved.

According to yet another feature of the present invention bytransferring waste heat energy to the low-boiling medium from thehydraulic oil that has increased in temperature as a result of loss ofenergy in the hydraulic circuit, the engine cooling water that hasincreased in temperature as a result of cooling the engine, and alsofrom the engine intake air that has increased in temperature as a resultof being compressed by the turbocharger, the hydraulic oil, the enginecooling water, and the engine intake air are cooled while thelow-boiling medium is vaporized. And by providing the turbine with thevaporized low-boiling medium through the low-boiling medium circuit inorder to drive the turbine so that the turbine provides a boost to theengine and thereby recovers the waste heat energy. As a part of the lostengine power, which would, in case of a conventional art, wastefullydissipate into the air as waste heat energy from the oil cooler, theradiator, and the intake air cooler, can be effectively recirculated tothe engine by means of the low-boiling medium circuit and the turbine,the energy use efficiency of the engine can be improved.

According to yet another feature of the present invention when a part ofthe low-boiling medium fed to the evaporator of the air conditioningdevice circuit installed in the construction machine branches off andpasses through the heat pipes, the waste heat energy of the hydraulicoil that has increased in temperature as a result of loss of energy aswell as the other fluid that has increased in temperature as a result ofoperation of the engine is transferred to the aforementioned part of thelow-boiling medium. As a result, the hydraulic oil and the other fluidare cooled while the low-boiling medium in the heat pipes is vaporized,the vaporized low-boiling medium is fed through the feed line to theturbine and thereby drives the turbine, and the low-boiling medium fromthe turbine is recirculated through the return line to the intake end ofthe compressor. As the configuration described above enables an airconditioning device circuit to be provided at lower cost by effectivelyusing a part of the air conditioning device circuit already incorporatedin the construction machine, eliminates the necessity of conventionalexpensive components, such as a cooling motor and a cooling pump fordriving a cooling fan, and also eliminates the power loss resulting fromdriving the cooling pump, the configuration described above is costeffective.

According to yet another feature of the present invention by using thepower transmission system, which branches off from the powertransmission unit that enables the engine to drive the pump, theconfiguration described above facilitates installation of the turbine.Furthermore, by driving the turbine by means of the low-boiling mediumvapor that has been vaporized by the waste heat energy from the oilcooler and the waste heat energy from the other cooling means, andfeeding driving torque generated in the turbine to the engine throughthe power transmission system, the configuration described above reducesthe driving power of the engine to drive the pump, thereby enablingreduction of fuel consumption by the engine, as well as effectiverecovery of thermal energy lost in the hydraulic circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fluid circuit diagram of a waste heat energy recovery systemaccording to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional hydraulic circuit.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is explained hereunder, referring to FIG. 1. Theelements similar to those of the conventional art shown in FIG. 2 areidentified with the same reference codes, and their explanation isomitted hereunder.

As shown in FIG. 1, a diesel engine (hereinafter simply referred to asengine) 11 is mounted on a construction machine, such as a hydraulicexcavator. The engine 11 is adapted to drive a pump, i.e. main pump 12,through a driving shaft unit 21 and an engine gear unit 22 that branchesoff from the driving shaft unit 21. The driving shaft unit 21 serves asa power transmission unit, and the engine gear unit 22 serves as a powertransmission system. In place of a conventional hydraulic cooling pump19, a steam turbine (hereinafter simply referred to as turbine) 24 isprovided for the engine 11. The turbine 24 is a small power recoveryturbine adapted to be rotated by means of energy provided by vaporizedlow-boiling medium (what is widely known as refrigerant) and isconnected to a shaft 23 of the engine gear unit 22.

The temperature of hydraulic oil increases and generates thermal energyas a result of loss of hydraulic energy from hydraulic output from ahydraulic circuit 25, which includes the main pump 12, theaforementioned energy loss being the remaining energy after subtractingthe energy consumed in the hydraulic circuit 25 for effective work. Asmost of this thermal energy passes through an oil cooler 16 a, which isa heat exchanger provided in a hydraulic oil return circuit 26, the oilcooler 16 a is adapted to cool the hydraulic oil that has increased intemperature.

As was the case with the oil cooler 16 a, other cooling means areprovided to cool other fluids whose temperature increases with operationof the engine 11. In the case of the present embodiment, the othercooling means are a radiator 16 b for cooling engine cooling water andan intake air cooler 16 c, such as an air-to-air after-cooler(hereinafter referred to as ATAAC), for cooling engine intake air.

To be more specific, similar energy loss also occurs in the coolingsystem of the engine 11, in which fossil fuel, such as diesel oil, burnsto generate energy to be supplied in the form of shaft power to the pumpsystem. Much of the energy that is not consumed as the shaft powerbecomes thermal energy and passes through the radiator 16 b, which isprovided in an engine cooling water circuit. Therefore, the radiator 16b is adapted to cool the engine cooling water that has increased intemperature due to cooling the engine 11, in other words, due to wasteof combustion energy in the engine 11.

Furthermore, when the engine intake air is compressed by a turbocharger(not shown) that is provided in an engine intake system, the temperatureof the engine intake air increases. Therefore, the ATAAC 16 c, which isprovided in an intercooler circuit, is adapted to cool the engine intakeair that has increased in temperature, thereby increasing the air intakeefficiency of the engine 11, as well as reducing its combustiontemperature so as to reduce the amount of nitrogen oxides generated.

A normal air conditioning device (hereinafter simply referred to asair-con) that is mounted on a construction machine, such as a hydraulicexcavator, has an air-con circuit 37, which may otherwise be referred toas an air conditioning device circuit comprises a compressor 32, acondenser 33, a receiver 35, a low-boiling medium pump 36, an expansionvalve (not shown), and an evaporator (not shown), all of which areserially connected to one another in an endless circuit. The compressor32 is adapted to be driven by a motor 31. The condenser 33 serves tocondense a low-boiling medium 34, such as a CFC substitute, by releasingheat from the low-boiling medium to the outside. The receiver 35 servesto retain the condensed low-boiling medium 34. The low-boiling mediumpump 36 is adapted to be driven by the aforementioned motor 31 so as tofeed the low-boiling medium 34 by applying pressure. The expansion valveserves to reduce pressure of the low-boiling medium 34. The evaporatorserves to cause the low-boiling medium 34 that is vaporizing afterpassing through the expansion valve to absorb heat from the outside. Asa conventional system has a circuit of this type, the air-con circuit 37is also shown in FIG. 2, which illustrates the conventional art.

Using the air-con circuit 37, a low-boiling medium circuit 38 thatincludes at least the oil cooler 16 a, the radiator 16 b, the ATAAC 16c, and the turbine 24 is provided to drive the turbine 24 by feeding thelow-boiling medium that has been vaporized by waste heat energyrecovered from the oil cooler 16 a, the radiator 16 b, and the ATAAC 16c.

The low-boiling medium circuit 38 includes heat pipes 41 a,41 b,41 c, afeed line 42, and a return line 43. A part of the low-boiling medium fedfrom the low-boiling medium pump 36 to the expansion valve and theevaporator of the air-con circuit 37, which is installed in the cab ofthe construction machine, is branched off from the air-con circuit 37and directed into the oil cooler 16 a, the radiator 16 b, and the ATAAC16 c through the heat pipes 41 a,41 b,41 c so that the low-boilingmedium vaporizes by absorbing heat from the hydraulic oil, the enginecooling water, and the engine intake air. The feed line 42 serves tofeed the low-boiling medium that has vaporized in the heat pipes 41 a,41b,41 c to the turbine 24. The return line 43 serves to return thelow-boiling medium from the turbine 24 to the intake end of thecompressor 32 of the air-con circuit 37.

Next, the function and effects of the embodiment shown in FIG. 1 isexplained hereunder.

In the hydraulic circuit 25 including the main pump 12, nearly all ofthe thermal energy generated as a result of loss of hydraulic energy atan actuator control valve 13, a relief valve 15, piping, and an actuator14 causes a rise in the temperature of hydraulic oil. The hot hydraulicoil passes the oil cooler 16 a, which is provided in the hydraulic oilreturn circuit 26. As described above, the heat pipe 41 a is providedinside the oil cooler 16 a so that the low-boiling medium 34, such as ACFC substitute, to be fed to the evaporator of the air-con circuit 37,which is installed in the construction machine, branches off the air-concircuit 37 and passes through the heat pipe 41 a. Therefore, instead ofconventional air cooling by a cooling fan 18 driven by a hydrauliccooling motor 17, the low-boiling medium reduces the temperature of thehydraulic oil and recovers thermal energy by removing heat from the hothydraulic oil in the course of vaporization by the thermal energy of thehydraulic oil in the oil cooler 16 a.

The aforementioned turbine 24 is connected to the engine gear unit 22,which is a power transmission system for enabling the engine 11 to drivethe main pump. By feeding the vaporized low-boiling medium to theturbine 24, the turbine 24 is driven by the low-boiling medium, and thedriving power of the engine 11 to drive the main pump 12 is reduced bythe driving torque generated in the turbine 24, thereby enablingreduction of fuel consumption by the engine, as well as effectiverecovery of thermal energy loss, the thermal energy loss being theenergy remaining after subtracting the energy consumed in the hydrauliccircuit 25 for effective work.

As described above, thermal energy is generated from the rise in thehydraulic oil temperature resulting from energy loss in the hydrauliccircuit 25, in which the main pump 12 is provided. The resulting thermalenergy is absorbed by the low-boiling medium, which vaporizes as aresult of absorption of the thermal energy. The vaporized low-boilingmedium rotates the turbine 24, and the rotated turbine 24 boosts enginepower. Thus, the energy is recovered.

In order to increase the energy use efficiency of the engine 11, it isdesirable to perform energy recovery with the oil cooler 16 a, radiator16 b, and ATAAC 16 c simultaneously, rather than with the oil cooler 16a alone.

This can be done by causing a part of the condensed low-boiling medium34 fed from the low-boiling medium pump 36 to the evaporator of theair-con circuit 37 to branch off from the air-con circuit 37 and passthrough the heat pipes 41 a, 41 b, 41 c, which are respectively providedin the oil cooler 16 a, the radiator 16 b, and the ATAAC 16 c, and, whenthe low-boiling medium 34 passes through the heat pipes 41 a, 41 b, 41c, cooling the hydraulic oil, the radiator water that has become hot,and the engine intake air by absorbing the heat generated from thehydraulic oil, the hot radiator water, and the engine intake air bymeans of vaporization of the low-boiling medium (refrigerant) 34 insteadof conventional air cooling by a cooling fan 18 (shown in FIG. 2).

At that time, the hydraulic oil that has increased in temperature in thehydraulic circuit 25 radiates its heat into the low-boiling medium inthe heat pipe 41 a of the oil cooler 16 a so that the low-boiling mediumvaporizes by absorbing the thermal energy of the hydraulic oil andthereby cools the hydraulic oil. At the same time, the radiator waterthat has become hot as a result of cooling the engine 11 radiates itsheat into the low-boiling medium in the heat pipe 41 b of the radiator16 b so that the low-boiling medium vaporizes by absorbing the thermalenergy of the hot radiator water, thereby cooling the radiator water sothat it can serve again as the cooling water. Simultaneously, the engineintake air that has increased in temperature as a result of beingcompressed by the turbocharger radiates its heat into the low-boilingmedium in the heat pipe 41 c of the ATAAC 16 c so that the low-boilingmedium vaporizes by absorbing thermal energy of the engine intake airand thereby cools the engine intake air.

By feeding the low-boiling medium that has vaporized in the heat pipes41 a, 41 b, 41 c to the turbine 24, which is connected to the shaft 23of the engine gear unit 22 and serves to retrieve driving force from theengine 11 to drive not only the main pump 12 but also other elements,the driving power of the engine 11 to drive the main pump 12 is reducedby the driving torque generated in the turbine 24.

For cooling the engine 11, in the place of a conventional hydrauliccooling pump 19 (FIG. 2), the turbine 24, which is a small powerrecovery turbine adapted to be rotated by the vaporized low-boilingmedium, is connected to the engine gear unit 22, which is a powertransmission system for enabling the engine 11 to drive the main pump.Therefore, the power loss by the engine 11 resulting from driving ahydraulic cooling pump 19 is mitigated.

As described above, in the place of a conventional hydraulic coolingpump 19, the turbine 24, which is a small power recovery turbine adaptedto be rotated by the vaporized low-boiling medium, is connected to theengine gear unit 22, which is a power transmission system for enablingthe engine 11 for a construction machine to drive the main pump, and theheat pipes 41 a,41 b,41 c are respectively provided in the oil cooler 16a, the radiator 16 b, and the ATAAC 16 c so that a part of thelow-boiling medium 34 to be fed to the evaporator of the air-con circuit37, which is normally installed in a construction machine, branches offfrom the air-con circuit 37 and passes through the heat pipes 41 a,41b,41 c. With the configuration as above, instead of air cooling by acooling fan driven by a conventional cooling motor, the system accordingto the invention vaporizes the low-boiling medium 34 by means of thermalenergy of the high temperature fluid in the oil cooler 16 a, theradiator 16 b, and the ATAAC 16 c so as to remove heat from the hightemperature fluid, thereby cooling the fluid and also recovering thethermal energy. By thus eliminating the necessity of conventionalexpensive components, such as a hydraulic cooling motor 17 and a pump 19for driving a cooling fan, the system according to the invention enablesreduction of production costs.

Furthermore, by causing a part of the low-boiling medium fed to theevaporator of the air-con circuit 37, which is installed in theconstruction machine, to branch off from the air-con circuit 37 and passthrough the heat pipes 41 a, 41 b, 41 c in the oil cooler 16 a, theradiator 16 b, and the ATAAC 16 c, the configuration of the embodimentenables the low-boiling medium to vaporize through absorption of wasteheat energy from the oil cooler 16 a, the radiator 16 b, and the ATAAC16 c. The low-boiling medium that has vaporized in the heat pipes 41a,41 b,41 c is fed through the feed line 42 to the turbine 24, fromwhich the low-boiling medium is recirculated to the intake end of thecompressor 32 of the air-con circuit 37 through the return line 43.Therefore, the configuration described above enables a low-boilingmedium circuit 38 to be provided at low cost by effectively using a partof the air-con circuit 37 already incorporated in the constructionmachine and adding the heat pipes 41 a,41 b,41 c, the feed line 42, andthe return line 43.

Furthermore, according to the invention, by using the engine gear unit22 serving as a power transmission system that branches off from thedriving shaft unit 21, by means of which the engine 11 drives the mainpump 12, a turbine 24 can be easily installed so that the low-boilingmedium that has vaporized in the heat pipes 41 a,41 b,41 c of the oilcooler 16 a, the radiator 16 b, and the ATAAC 16 c can be fed to theturbine 24, which is connected to the engine gear unit 22, by means ofwhich the engine 11 drives the main pump. The low-boiling medium vaporfed to the turbine 24 generates driving torque in the turbine 24, andthe resulting driving torque reduces the driving power of the engine 11to drive the main pump, thereby enabling reduction of fuel consumptionby the engine, as well as effective recovery of thermal energy loss inthe hydraulic circuit 25.

The features of the invention described above offer the followingbenefits.

It is possible to improve the energy use efficiency of the engine 11. Tobe more specific, it is possible to reduce the engine output to as lowas approximately 92% so that an engine one class lower can be used,enabling downsizing of the engine 11 and cost reduction.

Furthermore, by lowering the working temperature of hydraulic oil, it ispossible to extend the life of hydraulic oil and also to prevent thedecrease in viscosity of hydraulic oil, thereby extending the life ofsliding portions of hydraulic components.

Furthermore, the invention eliminates the necessity of such expensivecomponents as a motor and a pump for driving a cooling fan. Theelimination of such components not only enables downsizing and costreduction of the cooling unit but also eliminates such noise as windnoises of the cooling fan and prevents clogging of the heat exchangerthat would otherwise occur due to dust contained in the cooling air. Yetanother benefit of the invention lies in that the system of theinvention does not cause thermal pollution of the environment, becauseit does not radiate heat to the outside. Therefore, the inventionrealizes an environmentally-friendly cooling system.

According to the embodiment shown in the drawing, by means of the heatpipes 41 a,41 b,41 c passing through the oil cooler 16 a and othercooling means, i.e. the radiator 16 b and the ATAAC 16 c, thelow-boiling medium is vaporized by absorption of heat from the oilcooler 16 a, the radiator 16 b, and the ATAAC 16 c so that energy isrecirculated to the turbine 24. However, energy may be recirculated tothe turbine 24 by using other configuration to which the invention isapplicable; for example, the low-boiling medium may be vaporized byabsorption of heat from the oil cooler 16 a by using the heat pipe 41 apassing through the oil cooler 16 a, as well as absorption of heat byusing either one of the heat pipes 41 b, 41 c respectively passingthrough the radiator 16 b and the ATAAC 16 c.

INDUSTRIAL APPLICABILITY

The present invention is applicable to not only a construction machine,such as a hydraulic excavator, a bulldozer, or a loader, but also anyother machine provided with a hydraulic circuit that includes a pumpdriven by an engine.

1. A waste heat energy recovery method comprising steps of: using alow-boiling medium to absorb waste heat energy from hydraulic oil thathas increased in temperature as a result of loss of energy in ahydraulic circuit that includes a pump adapted to be driven by anengine, as well as waste heat energy from another that has increased intemperature as a result of operation of said engine, rotating a powerrecovery turbine by utilizing the low-boiling medium that has vaporizedas a result of absorbing the heat; and boosting power of said engine bymeans of said turbine.
 2. A waste heat energy recovery systemcomprising: an oil cooler for cooling hydraulic oil that has increasedin temperature as a result of loss of energy in a hydraulic circuit thatincludes a pump adapted to be driven by an engine; another cooling meansfor cooling another fluid that has increased in temperature as a resultof operation of said engine; a turbine for recovering driving power,said turbine provided for said engine and adapted to be rotated byenergy provided by a vaporized low-boiling medium; and a low-boilingmedium circuit serves to drive said turbine by providing said turbinewith the low-boiling medium that has been vaporized by waste heat energyfrom the oil cooler and the aforementioned other cooling means.
 3. Awaste heat energy recovery system as claimed in claim 2, wherein: saidother cooling means is a radiator for cooling engine cooling water thathas increased in temperature as a result of cooling said engine.
 4. Awaste heat energy recovery system as claimed in claim 2, wherein: saidother cooling means is an intake air cooler for cooling engine intakeair that has increased in temperature as a result of being compressed bya turbocharger.
 5. A waste heat energy recovery system comprising: anoil cooler for cooling hydraulic oil that has increased in temperatureas a result of loss of energy in a hydraulic circuit that includes apump adapted to be driven by an engine; a radiator for cooling enginecooling water that has increased in temperature as a result of coolingsaid engine; an intake air cooler for cooling engine intake air that hasincreased in temperature as a result of being compressed by aturbocharger; a turbine for recovering driving power, said turbineprovided for said engine and adapted to be rotated by energy provided bya vaporized low-boiling medium.
 6. A waste heat energy recovery systemas claimed in any one of the claims from claim 2 to claim 5, whereinsaid a low-boiling medium circuit comprises: heat pipes that permit apart of the low-boiling medium that is fed from a low-boiling mediumpump to an evaporator of an air conditioning device circuit to branchoff from said air conditioning device circuit and pass through said oilcooler and said other cooling means so that said low-boiling mediumvaporizes by absorbing heat from said oil cooler and said other coolingmeans, said air conditioning device circuit comprising a compressor, acondenser, a receiver, said low-boiling medium pump, an expansion valve,and said evaporator, all of which are installed in a constructionmachine and connected to one another in an endless circuit; a feed lineserving to provide said turbine with the low-boiling medium that hasbeen vaporized inside said heat pipes; and return line serving torecirculate the low-boiling medium from said turbine to the intake endof said compressor of said air conditioning device circuit.
 7. A wasteheat energy recovery system as claimed in any one of the claims fromclaim 2 to claim 6, wherein: said turbine is connected to a powertransmission system that branches off from a power transmission unitthat enables the engine to drive the pump.